Extreme pressure lubricant



United S sv Patent Helen Sellei Beretvas, Chicago, Ill.,. assigmor toStandard Oil Company, Chicago, 111., a corporation of Indiana NoDrawing. Application June 28, 1954, Serial No. 439,868

16 Claims. c1. zs2 37.2

This invention relates to novel lubricant compositions having especialutility under extreme pressure conditions. It is particularly concernedwith extreme pressure lubricants containing complex double soaps ofnaphthenic acid and certain low molecular Weight aliphatic carboxylicacids.

The use of oil soluble lead containing compounds, e. g. leadnaphthenate, lead olcate, etc. as components of extreme pressurelubricants is well known. Particularly outstanding extreme pressurelubricants have now been prepared which contain a double lead soap ofnaphthenic acid and certain low molecular weight aliphatic carboxylicacids including lactic acid, maleic acid, etc. By use of such leadsoaps, either alone or in combination with a simple lead soap such aslead naphthena'te, the extreme pressure properties of lubricating oilscontaining sulfur and usually chlorine containing E. P. additives(extreme pressure additives) may be greatly improved over thatobtainable with a simple soap alone. And it has been found that for agiven weight of soap the amount of lead introduced to the oil can beincreased by using the novel complex soaps instead of a simple soap, e.golead naphthcnate. Moreover, the properties of complex soaps have beenfound to be substantially more consistent and not subject to theWidevariation experienced with commercial lead naphthenate purchasedfrom several dilferent suppliers.

The lowmolecular weight a-lip'haticcarboxylic acids suitable for use inaccordance herewith are those containing from two to about six andpreferably three or four carbon atoms. Acids having either a hydroxygroup attached to one of the carbons in the chain or those havingadouble bond in the linear carbon chain may be used. Such compounds maybe monoor di-carboxylic and typical examples thereof are: g'lycolicacid, lactic acid, maleic acid, malic acid, citric acid, 7 hydroxybutyric acid, a hydroxy butyric acid, etc.

Whereas certain low molecular weight carboxylic acids have beenenumerated above, these are for purposes of illustration and not oflimitation. And it should be undcrstood that those compoundsfallinggenerally within the broad definition of the useful class of compoundsmay be employed.

lit accordance herewith, basic lead naphthenate is preferablyreactedwith litharge and a low molecular weight acid to produce the complexsoap of the present invention. Naphthenic acid may, of course, be usedin such reaction instead of the soap. The so-called basic leadnapht'henate is an available article of commerce which is incompletelyconverted to the totally neutralized soap and is therefore usually moreexpedient to employ since half-the double complexsoapis, in effect,already for-med. The present invention will, accordingly, be describedwith respect to such preferred method of preparation. Itis theoreticallypossible that the reaction may begin with n-aphthenic acid and the soapof the low molecular weight acid, e, g. lead lactate, to obtain theresultant complex double soap, but the oilinsolubility of the lowmoleculat weight soap and consequent inferior contact in the reactionzone make such method less desirable. Saponification resulting in thecomplex soap may be preferably initiated by a small amount of caustic orpotash which may be added in pellet or other form in small amount, e. g.from about 0.05 to about 2% by weight.

The manner in which the double soap is prepared is not of itself a partof the invention and although it has been found as a practical matterthat the double soaps are best prepared in accordance with the techniquedetailed, other methods resulting in the soap may, of course, beemployed. Especially, however, in connection with the introduction ofmore than the theoretical (or stoichiometric) amounts of lead or lacticacid, as will hereinafter be discussed, the technique described hereinhas been found most satisfactory. The preparation of basicleadnaphthenate'is, of course, well known to those skilled in the artand is in no way a part of the instant invention. The generally greatereffectiveness of lead fish oil soaps as extreme'pressure additives ascompared to lead naph thenate is believed to be related to the relativeoil-insolu bility of the former. Accordingly, efforts to improve theeffectiveness of the lead naphthenate have resulted in the discoverythat complex soaps embodying a low molecular weight acid radical aresubstantially less soluble in oil and vastly superior in their extremepressure properties to lead naphthenate. Thus, it would appear that theleast soluble complex soap which may, however, still be dispersed ordissolved in a lubricating oil is the most satisfactory. Because the lowmolecular weight acids em pl'oyed decrease oil solubility of thecomplex, the larger the amount of such acid in the complex the lower thesolubility of the same for a given weight of soap and the more improvedare the extreme pressure properties. However, the desire for a ratherinsoluble lead soap must be tempered by the necessity of keeping theadditive in the oil, i. e. producing a stable lubricant. In thisconnection, it has been found that oleic acid or an alkyl phenol, e. g.nonyl phenol or other alkyl phenols hav- "ing a total of from about 8 toabout 12 and preferably about 9 or 10 carbon atoms in no more than twoalkyl side chains and no such side chain containing fewer thanfourcarbon atoms, is especially effective in solu'biliz-ing complexdouble soaps which are ditficultly soluble. The alkyl phenol may beemployed in an amount of from abouttlS-to about 10% and preferably fromabout l'to about 6%. Moreover, solvent extracts, e. g. phenol, furfural,Ghlorex, etc., of lubricating oils and other petroleum fractions arealso excellent solubilizers for use in accordance herewith. From about 1to about 50% by weight or more and preferably from about 2 to about 3 0%of extract solu'bilizer may be used. Lead naph- "theriate is itself auseful solubilizing agent and is especially advantageous from thestandpoint of introducin'g still more lead to the lubricant.

As will be apparent from data set forth in Table 1, oleic acid hasespecial utility in extreme pressure lubricants of the type hereindescribed over and above its more solubili'zing influence upon thecomplex soap. This higher molecular weight unsaturated carboxylic acidhas been shoW-n'to substantially improve the extreme pressure propertiesof such an oil. And, in accordance with a preferred lubricantcomposition of the present invention, there is employed in conjunctionwith the complex soap and a sulfurized and chlorinated E. P. additive,at least about 1% oleic acid, by weight, based upon tot-allubricant andpreferably from about 2 to 7%. As much as 10% or more may be used butthe resulting improvement, if any, compared to cost is ordinarily notjustifiable.

I-n accordance with the preferred embodiment of the present invention,the complex double soaps are prepared by combining litharge and basiclead naphthenate in a ratio of from about 1:1 to about 1:6 parts, byweight, and preferably about 1:4. The low molecular weight acidcomponent of the double soap is employed in an amount of from about 1 toabout moles of low molecular weight acid per mole of litharge andpreferably from about 1 to about 2. More lactic acid may be used; it isdoubtful that the same will combine in a stable manner and is,accordingly, unnecessary.

Thus, for example, 100 parts, by weight, of a commercial basic leadnaphthenate (containing 30% lead) are reacted with from about to about65 parts of litharge, and preferably about 1 part of litharge to every 4parts of basic lead napthenate, and from 1 to 5 moles of low molecularweight acid, e. g. lactic acid, per mole of litharge. Preferably, about1 to 2 moles of low molecular weight acid per mole of litharge areemployed although larger amounts of litharge may be employed.

It will be apparent that in the event of employment of the large amountsof reactants in the upper ends of the above defined ranges, there willof necessity be substantially more than the theoretical stoichiometricquantity required for the formation of double soaps having the formulaRCOOPbOOCR, wherein R represents the radical of naphthenic acid and Rrepresents an acyclic radical of the particular low molecular weightacid. As will appear from data hereinafter presented, soaps containingsuch an excess have been found especially desirable but it is notunderstood in just what manner such an excess contributes to theexcellent results obtained. For this reason, the double soaps aresometimes referred to herein as complex lead soaps or complex doublesoaps in order to emphasize the existence in certain instances of astable excess of lead and/or low molecular weight acid. The theoreticaldouble soap, i. e. containing no excess is, of course, included withinthe meaning of such terms. These excesses are believed to be held in thedouble soap inthe form of a chemical complex.

The preparation of the complex double soap is preferably carried out ata temperature in the range of from about 240 F. to 320 F. but a broaderrange of temperatures, for example, from about 200 F. to about 400 F.may be employed.

-. Complex double soaps of the present invention are primarily useful inheavier mineral lubricating oils of the type employed for extremepressure use, e. g. lubricating oils having a viscosity at 210 F. of atleast about 50 S. S. U. and preferably about 75 to about 115 S. S. U.The soaps are not limited in their. utility to such oils, however, andmay be used with oils having lower as well as higher viscosities. Suchoils may be acid treated, solvent extracted, etc. without in any waydeparting from the scope of this invention. Non-solvent extracted, acidtreated (sulfuric acid) oils are preferred for use in accordanceherewith.

The amount of the novel soaps, described herein, which may be employedin extreme pressure lubricants will vary over a rather wide rangedepending upon the type of oil, the other additives employed, theintended application of the particular lubricant, etc., but generally anamount of from about 1 to about. 10%, by weight, based on totallubricant and preferably from about 3 to about 7%, by weight, has beenfound desirable.

For the purpose of illustrating the preparation of the novel complexsoaps of the present invention but with- .out any intention of beinglimited to the specific illustrative examples set forth, the followingexamples are presented:

Example 1 Three hundred grams of commercial basic lead naphthenate(approximately 30% lead) were reacted with of the active acid) was added(the mole ratio, of PbO to lactic acid being about 1:2) in about 5minutes and the temperature dropped to 230 F. Reaction was apparentlycomplete in about 7 minutes, but stirring was continued for about anhour during which time the temperature slowly dropped. The resultingproduct was quite hard and contained about 36% lead.

Example 2 Commercial basic lead naphthenate (30% lead) in an amount of19.8 pounds was mixed with 5% pounds of lactic acid (80%-technicalgrade) and heated to 240 F. 68 grams of potassium hydroxide pellets wereadded along with 4.8 pounds of litharge. These materials were added inabout half an hour and the temperature rose to 310 F. The mixture wasthen stirred for about 3 hours at 300 F. and the heat was then shut ofi.To the hot product (at about 300 F.) was then added 16 pounds of oleicacid and the mixture was then stirred for about one-half hour. The leadcontent of the product before the addition of oleic acid was 36.2%. ThePb content of the blend was 22%.

Example 3 Three hundred grams of commercial basic lead naphthenate 30%lead) were mixed with 150 grams of lactic acid (80%-technical grade) andheated to about 240 F. A relatively small amount of potassium hydroxidepellets were added to initiate saponification while adding grams oflitharge. The ratio of litharge to lactic acid on a mol basis was about1:4. The reaction was complete in about half an hour and the temperaturerose to about 300 F. as in Example 2. Stirring was continued for severalhours and the heat was then turned off. The complex soap which comprised35.5% lead by weight was then blended with oleic acid in a 60% soap- 40%oleic acid ratio in order to prepare a material readily soluble in thelubricating oil.

Example 4 Three hundred grams of commercial lead naphthenate (30% lead)were mixed with grams of maleic acid and heated to about 240 F. 5potassium hydroxide pellets were added along with 75 grams of lithargeand the temperature rose to about 300 F. Reaction was over ratherquickly but stirring was continued for approximately two hours. Thecomplex soap contained 40.9% lead and was then blended with oleic acidto give a somewhat ditficultly soluble additive for lubricating oils.

In order to determine, in the laboratory, the effectiveness of thecomplex double soaps prepared in accordance with theforegoing examples,tests were run in both the Timken and Shell four-ball extreme pressuretesting machines. Each of these testing machines is useful in thelaboratory evaluation of extreme pressure lubricants, but they aredissimilar in their method of testing and in the results obtainabletherefrom. Thus, oils will often show up well on one test but noton theother. However, lubricating engineers, while not entirely in agreementas to the exact meaning of these tests when translated into actualperformance, have been able to correlate these tests to a certain extentand, in general, find them most helpful in evaluating new lubricantcompositions. Field tests in the rear axle gears of at least one majorautomobile manufacturer have resulted in adoption of extreme pressurelubricants of the type herein described.

The Timken machine and test are well known to those skilled in the art,and it is, unnecessary here to describe the same in detail since theyare fully described in the Journal of the Institute of Petroleum 32, pp.209-210 and 220-222 (1946). The Shell four-ball testing machine islikewise well known to those skilled in the art for its utility inevaluating hypoid lubricants and is likewise described in detail in theliterature National Petroleum News 31, 52 (December 27, 1939) p. R551and also Journal of the Institute of Petroleum 32, pp.-21-0-21 2 and Setforth in Table 1 are the results of tests in the Timken machine whichdemonstratet-he improvementobtained by employing the novel soaps of thepresent inventionincomparisonwith the use of lead naphthenate. .In eachof the testsnset forth in Table 1,,alubricant base comprising anon-solvent extracted S. A. E. 50 grade mineral. oil containing 5%, byweight, of sulfurized sperm oil (.10 to 1.3% sulfurr), 3% of achlorinated hydrocarbon (-73% chlorine wasemployed. The ultimatelubricant in each instance had aviscositywat 2l0 F. of between. about 80*and'98 S. S. U.

TABLE 1 1 F 1 iimen L'lesdt Percent esu s, on RunNb. Nliiihuieni" 3 23;3333 Lbs.

F igg Complex Acid Tires Fail 5 it None None 35 40 5 i None 2 451: 50 6None 4 50 55 4.2 None 13.8 55: 60 None 5 None 65 70 None "3 '4 65 70None 5 2 75 B 1. b 1. 5 2 70 75 N one =4: 2 15.8 70 '75 None 4; 2 6. :875 80 None A 452 6. 8 80 '85 None 4 14.2 6. 8 80 85 I Complex soapemployed was made in accordance'with method of ustrative Example 1,supra, no oleic .acid was employed to solubilize th'e'compiex.

Complex soap employed was unade in accordance with method ofillustrative Example 1,.supra, and then blended with an equal amount ofPb naphthenate"(30% Pb).

I Sample of complex soap omployedwas that prepared in :ExampleB, supra,2.8% oleic acid was combined with the soap initially to render the samereadily soluble and 4% additional oleic acid was added to finalubricant.

4 Sample of complex soap employed was that prepared in illustrativeExample 4, supra, 218% ct oleic acid added tosoaplnitially and 4%additional as in 1 Complex soap employed was made in accordance withmethod of illustrative Example 2, supra, 2.8% of oleic acid added tosoap initially and "4% additional -as in The striking improvement in theTimken results when employing a novel complex of the present inventionis demonstratedby the above table. The advantage of the complex soapover the lead naphthenate, either alone or in the presence of oleicacid, is obvious.

Additional tests in the Shell four-ball tester further demonstratetheimprovement obtained with the complex as compared to lead naphthenate.In these tests in order to demonstrate the effectiveness of the complexin the absence of sulfurized or chlorinated materials, only thosematerials noted in the table were present in an acid treated S. A. E. 50base oil and no sulfur or chlorinated materials were employed.

The above data indicate the improvement obtainable with the complex soapand demonstrate, in a second test, the improved results obtainable withthe lead complex soap. Whereas the use of oleic acid results in noapparent improvement as evidenced in the Shell four-ball test, it wouldappear to merely be further confirmation of lack of correlation betweenthe various extreme pressure tests.

Although the specific materials employed in the tests set carbons andorganic materials.

. g I a forth Table l were a sulfurized sperm oil and a chlorinatedhydrocarbon, it should be understood that many other known sulfur and/or chlorine-containing materials may be employed in conjunction with thelead complexes of the present invention. Thus, sulfurized hydrocarbons,sulfurized carboxylic acids, e. g. sulfurized tall oil, sulfurized oleicacid, etc., organic sulfides, sulfurized vegetable oils, polysulfides,e. g. the dialkyl tri-, tetra-, pentaand hexasulfides, and otheroil-soluble: sulfur-containing compounds or materials useful in extremepressure lubricants, may be employed alone or in combination with eachother, in accordance herewith. Reference is made to U. S. 2,136,391,2,202,394, and many other patents disclosing sulfur containing additivesfor extreme pressure addition; such materials are generally useful inaccordance herewith. Such sulfur-containing organic constituents aregenerally employed in the extreme pressure lubricant in an amountsuflicient to afford a lubricant sulfur content of from about 0.3 toabout 5.0%. Thus, an amount of sulfur-containing organic E. P. additiveof from about 1 to about 20% and preferably from about 3 to about 15%may be employed. Likewise, chlorinated compounds of various types may beemployed in lubricants containing the novel complexes. Thus, chlorinatedhydrocarbons have been employed which, for example, may be obtained bychlorinating paraffin wax or olefinic hydrocarbons. Individualchlorinated aliphatic compounds such as hexachlorethane,heptachlorpropane, octachlorbut'ane, etc. are useful. Reference is madeto U. S. 2,178,513 which sets forth a substantial number of halogenatedorganic ring compounds which are useful in extreme pressure lubricants.Such materials may be em- .ployedin accordance with the presentinvention. U. S. 2,276,341 discloses. large numbers of chlorinatedhydro- These also may be employed in accordance herewith. Thechlorine-containing E. P. agents or additives are employed in thepresent extreme pressure lubricants in an amount sufficient to afford alubricant content of from about 0.38.0% preferably from about 1% toabout 3% of chlorine. An amount of chlorine-containing organic E. P.additive of from about 1% to about 10% and preferably about 2 to about8% may be employed.

In addition to the sulfurized, chlorinated and lead-conmin ng materialsdisclosed hereinabove, it should be understood that lubricantscontaining the same may also have added thereto typical lubricating oiladditives such as antioxidants, oiliness agents, corrosion inhibitors,detergents, etc. In particular, phosphorus-containing compounds oftenemployed in extreme pressure lubricants may be employed. A particularlyuseful phosphorus-containing material is that resulting from thetreatment of a hydrocarbon, e. g. an olefin polymer, with a phosphorussulfide. Other phosphorus containing compounds, useful in lubricants ofthis kind, may also be employed.

As indicated above, lead naphthenate may be employed in addition to thelead complexes of the present invention. Likewise, other lead soaps suchas lead oleate, lead tallate, and lead soaps of various high molecularweight oilsoluble carboxylic acids which do not substantially affect theviscosity of the lubricant, i. e. do not substantially thicken or gelthe lubricant, may be employed in conjunction with the novel complexesof the present invention. Moreover, the lead soaps may themselves besulfurized lead tallate, sulfurized lead naphthenate, etc. and used inconjunction with the complex soaps of the present invention.

Percentages recited herein and in the appended claims are by weightunless otherwise indicated.

Having thus described my invention what I claim as novel and desire toprotect by Letters Patent is set forth in the following claims:

1. A normally liquid extreme pressure lubricant comprising a minerallubricating oil and a minor amount of a complex double soap having thegeneral formula RCOOPbOOCR wherein R represents a naphthenic acid'radical and R represents the acyclic radical of a carboxylic acidcontaining from 2 to about 6 carbon atoms which carboxylic acid isselected from the group consisting of unsaturated carboxylic acids andhydroxy carboxylic acids.

2. The lubricant of claim 1 wherein the low molecular weight carboxylicacid is lactic acid.

3. The lubricant of claim 1 wherein the low molecular weight carboxylicacid is maleic acid.

7. A lubricant comprising a mineral lubricating oil and 1 from about 1to about 10% of a complex double soap having the general formulaRCOOPbOOCR' wherein R represents a naphthenic acid radical and Rrepresents the acyclic radical of a carboxylic acid containing from 2 toabout 6 carbon atoms which carboxylic acid is selected from the groupconsisting of unsaturated carboxylic acids and hydroxy carboxylic acids.

8. A lubricant comprising a mineral lubricating oil, an

amount of sulfur-containing organic material effective to improveextreme pressure properties of said lubricant, and from about 1 to about10% of a complex double soap having the general formula RCOOPbOOCR'wherein R represents a napthenic acid radical and R represents theacyclic radical of a carboxylic acid containing from 2 to about 6 carbonatoms which carboxylic acid is selected from the group consisting ofunsaturated carboxylic acids and hydroxy carboxylic acids.

9. The lubricant of claim 8 wherein the sulfur-containing organicmaterial is a sulfurized sperm oil.

10. The lubricant of claim 8 which includes an amount ofchlorine-containing organic constituents effective to improve theextreme pressure properties of said lubricant. 11. The lubricant ofclaim 8 which includes from 1 to about 10% of oleic acid.

12. The lubricant of claim 8 which contains from about 1.5 to about 50%of a solvent extract of a mineral lubricating oil.

13. The lubricant of claim 8 which contains from about 1.5 to about'50%of a solvent extract of a petroleurn mineral oil and from about 0.5 toabout 10% of an alkyl phenol containing a total of from about 8 to about12 carbon atoms in no more than two alkyl side chains, with no such sidechains containing less than four carbon atoms.

14. The lubricant of claim 8 which contains from about 0.5 to 10% of analkyl phenol containing a total of from about 8 to about 12 carbon atomsin no more than two alkyl side chains, with no such side chainscontaining less than four carbon atoms.

15. The lubricant of claim 14 wherein the alkyl phenol is nonyl phenol.

16. An extreme pressure lubricant composition comprising essentially amajor proportion of a mineral lubricating oil and thefollowingconstituents in the following approximate weight percentagesz'Per cent Complex double soap 3 to 7 Organic sulfur-containing E. P.additive 3 to 15 Organic chlorine-containing E. P. additive 2to 8 Oleicacid t 2 to 7 Alkyl phenol 1 to 6 References Cited in the file of thispatent UNITED STATES PATENTS 1,781,167

Doell Nov. 11, 1930 2,163,622 Neeley et al: June 27, 1939 2,455,892Fraser Dec. 7, 1948 2,595,566

Worth et a1. May 6, 1952

1. A NORMALLY LIQUID EXTREME PRESSURE LUBRICANT COMPRISING A MINERALLUBRICATING OIL AND A MINOR AMOUNT OF A COMPLEX DOUBLE SOAP HAVING THEGENERAL FORMULA RCOOPBOOCR'' WHEREIN R REPRESENTS A NAPHTHENIC ACIDRADICAL AND R'' REPRESENTS THE ACYCLIC RADICAL OF A CARBOXYLIC ACIDCONTAINING FROM 2 ABOUT 6 CARBON ATOMS WHICH CARBOXYLIC ACID IS SELECTEDFROM THE GROUP CONSISTING OF UNSATURATED CARBOXYLIC ACIDS AND HYDROXYCARBOXYLIC ACIDS.